1. Field of the Invention
The present invention is directed to leveller combinations based on poly(meth)acrylic acid esters and silicones for high-solids polyurethane reactive coating systems containing blocked isocyanate-terminated prepolymers and polyamines.
2. Description of the Prior Art
High-solids PU reactive systems of blocked NCO-prepolymers which are reacted with preferably aliphatic and/or cycloaliphatic polyamines in the coating process to form polyurethane ureas, the blocking agent being eliminated on heating, are known. The production of systems such as these and the coating of textile substrates by the transfer and direct coating processes are described, for example, in DE-A No. 2,902,090 (EP-A No. 13,890), according to which the coating systems may also contain levelling aids, such as polydimethyl siloxanes or polyoxyalkylene/polydimethyl siloxane copolymers.
The difficulties in the form of blisters, bubbles and levelling faults encountered in the direct coating of blocked, high-solids, PU reactive systems onto textile substrates, such as woven fabrics, knitted fabrics and nonwovens of a variety of fiber materials, particularly on both sides, are avoided by the process according to the present invention.
The process according to the invention for coating textile substrates on one and, more particularly, both sides or for mold copying with blocked high-solids NCO prepolymers, the reactive systems being crosslinked with polyamines, is characterized by the simultaneous addition of vinyl polymers and polysiloxanes and/or vinyl graft polymers based on polysiloxanes as levelling and homogenizing agents.
The effect of blister-free and bubble-free coatings obtained by these combined additions, particularly in the case of two-sided coating with high-solids PU reactive systems, was surprising and was not suggested by any previous experience or by any disclosures in the literature. The favorable levelling behavior of the high-solids PU reactive systems is also of advantage in the coating of molds, for example for the production of velour leather in accordance with German Pat. No. 3,004,327.